The demonstration that improved metabolic regulation of the insulin dependent diabetic will significantly affect the development of the chronic complications of diabetes will have major clinical and pathophysiological significance. However, to date this contention remains unproven. The recent availability of more appropriate means of insulin replacement and the prospect of a collaborative controlled randomized prospective trial addressing "the relationship between blood glucose control and the vascular complications of Insulin Dependent Diabetes Mellitus" may resolve this controversy. In accordance with the guidelines outlined in the RFA, we have obtained the full administrative, academic, and clinical support of the Toronto General Hospital and Hospital for Sick Children with the aim of establishing a clinical center for this program in Toronto. Suitable diabetic patients meeting the inclusion criteria will be recruited into the trial, and randomized to either "conventional" or "strict" metabolic control. "Strict" control will be achieved by the technique of subcutaneous insulin infusion using the autosyringe (Model AS-6C) coupled with home glucose monitoring. "Conventional" treatment will consist of one or two depot insulin injections adjusted to obtain the best possible control. Diet instruction, diabetic teaching and follow up will be identical in both groups. A "conventional" treatment group with home glucose monitor may have to be established to evaluate the role of this technique in achieving improved metabolic regulation in a controlled trial. To assess the metabolic response to treatment and the feasability of obtaining two destinct levels of control, plasma glucose, glycosylated hemoglobin, plasma lipid 24 hr. urinary glucose, and meal metabolite and hormone profiles will be measured at defined intervals. Methods for assessing the complications of diabetes (ophthalmologic, neurologic and renal) will be established and further evaluated during the limited randomized trial so as to be uniformly applied during the full scale clinical trial. A comprehensive team approach (physician, nurse coordinator, dietitian, diabetes educator and psychologist) for out-patient surveillance will be established to monitor the response to the treatment protocols, as well as possible adverse reactions.